1. Field of the Invention
The present invention is related to railway vehicles having a variable trim body, of the type comprising two bogies with respective frameworks and swinging transverse members, resilient suspension means between the frameworks of the bogies and the respective swinging transverse members, articulated connection means between each swinging transverse member and the body, and a body roll control system comprising actuator means interposed between said swinging transverse members and the body, a regulation electronic unit operatively associated to said actuator means, and first and second transducer means for detecting respectively the non-compensated centrifugal acceleration acting on the vehicle body and the running condition of the vehicle along entry and exit curve transition sections, and for transmitting corresponding output signals to said regulation electronic unit to pilot said actuator means so as to perform, while the vehicle is running along a curve, rotations of the body around its longitudinal axis tending to compensate said centrifugal acceleration.
The rotation or roll of the body carried out by the control system of the vehicle allows, particularly as far as high-speed railway vehicles are concerned, appreciably enhancing comfort for the passengers, due to the fact that the transverse acceleration felt within the body as the vehicle is running over a curved track is relatively limited.
2. Description of the Prior Art
U.S. Pat. No. 3,844,225 assigned to Fiat Spa discloses a body roll control system for a railway vehicle of the above-referenced type, wherein the first transducer means for detecting the centrifugal acceleration acting on the body comprise an accelerometer. Since the output signal of the accelerometer is hugely disturbed by the transverse motions of the vehicle even during straight travel, owing to hunting phenomena, it is necessary to filter the accelerometer output signals at very low frequencies so as to avoid unacceptable succession of undesired interventions of the body roll control system. This involves as a consequence a delay in the transmission of the actual control for the body rotation, and a reduction of the available time for carrying out the trim variations.
In order to limit such a delay, the above referenced U.S. patent provides employing a gyroscope detecting transverse tilting of one axle of the vehicle front bogie, as the latter enters the parabolic entry and exit transition sections of the track curves. Such tilting is due to the fact that along these parabolic transition sections the outside rail of the track is gradually raised or superelevated relative to the inside rail until reaching its maximum height in the constant-radius curve section, and then returning to the level of the inside rail at the end of the exit transition section.
The gyroscope devices are however affected by the drawback of being delicate and thus of short operation life, as well as expensive, and moreover require complex treating and conditioning circuits of the relative output signals.
To the aim of avoiding the above drawback, Italian patent No. 1.071.565 in the name of Fiat Ferroviaria Savigiiano Spa has proposed to employ, instead of a gyroscope, an angle transducer adapted to detect the momentary relative angle formed in a transverse plane between at least two axles of the vehicle and to generate a corresponding output electrical signal, proportional to said angle, which is fed to the body roll control system.
The advantages deriving from using an angle transducer mainly reside in that such a transducer is less expensive, more resistant and thus affording a longer operation life with respect to the gyroscope, while ensuring at the same time a sufficient output signal promptness.
The solution according to the above-referenced Italian patent contemplates applying the angle transducer directly between two axles of a same bogie, or between two axles belonging to the one and to the other bogie, respectively.
In either case mounting of the angle transducer is constructively complicate; since it involves employing transmission shafts and related universal and telescopic joints between the inductor and rotor members of the angle transducer. Moreover, in both cases the signal of the angle transducer is quite negatively affected, i.e. fouled, by the motions of the secondary suspension interposed between the bogies and the body of the vehicle.